The overall goal of this Project is to investigate the role of "regulatory" cytokines, interleukin-4 (IL-4), transforming growth factor beta (TGFbeta) and interleukin-10 (IL-10), on the pathophysiology of insulin-dependent diabetes mellitus (IDDM) in the non-obese diabetic (NOD) mouse and to adapt this strategy to human T cell clones in vitro. This goal is based upon recent literature which suggests that Th-1 T cells act as proinflammatory disease-inducing cells in animal models of autoimmunity whereas Th-2-like cells seem to be "counter-regulatory." Recent studies of mice with experimental autoimmune encephalomyelitis (EAE) demonstrated that disease-suppressing T cell clones could be generated by oral tolerance induction and that such clones, although using the identical T cell receptor as disease-inducing clones, secreted "regulatory" cytokines TGFbeta, IL-4 and IL-10. Studies outlined in this project seek to explore the therapeutic potential of "regulatory" cytokines by transferring the genes that encode these cytokines individually or in combination into NOD T cell clones for adoptive transfer and, if successful, to use targeted gene delivery to transduce inflammatory CD4+ OX-40+ T cells, in vivo, in islets of NOD mice. This project contains five specific aims including: 1) the development of retroviral vectors for transfer of selected cytokine genes to NOD and human T cell clones; 2) transduction of autoantigen- reactive NOD and human T cell clones with these genes; 3) demonstration that adoptive transfer of the transduced NOD clones prevents or ameliorates diabetes in NOD mice; 4) generation of OX-40 ligand containing retroviral vectors for use in vitro and in vivo and transduction of T cell clones in vitro; and 5) targeted transduction of activated T cells in NOD insulitis lesions in vivo. The results should demonstrate that the delivery of specific cytokines to pancreatic islets can be used as the basis for a tissue-specific locally effective immunotherapeutic approach to the treatment of diabetes.